Bi-directional switches switch high currents through their conduction electrodes while blocking high voltages applied to the conduction electrodes. Bi-directional switches are used in a variety of electrical systems. A typical bi-directional switch is specified to supply high currents, which may range from several Amperes of maximum current to several hundreds of Amperes depending on the specific switch and application, while blocking relatively high voltages, e.g. of at least 25 V without breaking down.
Bi-directional switches are typically implemented using electromechanical switches or a configuration of semiconductor devices, e.g. power transistors. However, standard power transistors have a low blocking voltage in one direction, making them unidirectional devices. Consequently, current bi-directional switches typically are implemented using two separate serially coupled power MOSFETs. The separate MOSFETs are formed on separate semiconductor dice, and often housed in separate packages, which results in a high manufacturing cost and a large area occupied on a circuit board. When the separate MOSFET dice are housed in a single package and interconnected with wire bonds, the area occupied on a circuit board is reduced but the manufacturing cost is still too high for many applications.
U.S. Pat. No. 8,101,969 discloses an integrated circuit with several different transistors integrated on the same circuit, including a p-channel bi-directional trench power transistor for battery charging protection. The transistor comprises two vertical trenches between which a body is present. The body is separated from current carrying electrodes above and below the body by high-voltage regions with a lesser doping concentration than the electrodes.
However, a disadvantage of the bi-directional trench power transistor disclosed in U.S. Pat. No. 8,101,969 is that it exhibits a potential to breakdown unexpectedly. Furthermore, it exhibits a slow switching behaviour.